The subject matter disclosed herein generally relates to heat transfer systems and, more particularly, to heat transfer systems that include an aluminum surface in contact with a heat transfer fluid.
Heat transfer systems are widely used in various applications, including but not limited to heat transfer systems for environmental heating and cooling in aerospace applications, automotive, industrial, residential, and electronics, to name a few. Heat transfer systems often utilize a heat transfer fluid that circulates between two or more heat exchangers to transfer heat between environmental spaces. Many such heat transfer systems include one or more aluminum components in contact with the heat transfer fluid. Aluminum alloys offer durability, malleability, high strength to weight ratio, and thermal conductivity, which make it a desirable material for heat transfer system components such as heat exchangers, tubes, fins, etc.
Many different types of heat transfer fluids have been used or proposed for use in various types of heat transfer systems. Organic liquids such as halogenated hydrocarbons (e.g., R-134a (tetrafluoroethane), R-1234 (tetrafluoropropene)) have been used in many systems. However, such fluids, although they offer improvements over prior chlorinated fluorocarbons, are still subject to toxicity, flammability, lower thermal performance than water, and environmental issues. Additionally, they are often not suitable for use in heat transfer systems in enclosed environments such as aerospace or submarine environments, where leaks or other accidental release into the enclosed environmental space would be problematic from an occupant health perspective. Aqueous-based heat transfer fluids containing glycols such as propylene glycol have also been used. Such fluids can provide benefits over organic liquids with respect to toxicity, flammability, thermal performance and environmental issues. However, they are not suitable for some heat transfer systems, especially those with a high surface area of aluminum, where corrosion becomes a challenge. For example, propylene glycol acts to reduce the freezing point temperature of the heat transfer fluid. In PCM (phase change material) heat transfer systems where the latent heat of a phase change material is used to store and release thermal energy, the freezing point suppression imparted by the glycol to an aqueous heat fluid can be problematic. In other systems, such as capillary coolant systems used for cooling lasers or heat-generating manufacturing tools, the glycol may have a detrimental effect on the surface active properties of the coolant needed for proper capillary action. Also, the use of aqueous based coolants results in a need to control microbial growth.
Although the above-described and other heat transfer fluids can be effective in various applications, new and different alternatives are always well received that might be more appropriate for or function better in certain environments or could be less costly or more effective.